The process took 1 day. I interviewed at Deloitte (Phoenix, AZ) in Oct 2011
Interview
I first arrived at the interview on my university's interviewing site and was greeted by a Deloitte greeter. She was very friendly, and we chatted about various topics. My interviewer, then, came out of the room and greeted me. The interview I did not feel was very formal. He was extremely nice, and wanted to know what I had questions about regarding the position. It was more of an informative interview rather than asking direct questions to me. He made is seem like a natural conversation rather than an interview.
I applied online. The process took 1 day. I interviewed at Deloitte (Diegem, Flemish Brabant) in Nov 2009
Interview
Had a short phone interview that asked about my motivation to choose for applying at Deloitte. I was also asked a question about some elements in my resume, after which I was invited to the assessment day.
The assessment consisted of a group case (5 people). We had 20 mins to read through the material, then 1 hour to discuss and another 30 mins to prepare the presentation. After the presentation there was a short group interview about the case.